Tube forming apparatus



Dec. 27, 1949 Filed Dec. 30, 1947 R. B. THOMAS ETAL 2,492,904

TUBE FORMING APPARATUS 2 Sheets-Sheet l GERALD QUINN A'rroe NEY R. B,THOMAS ET AL Dec, 27, 1949 2 Sheets-Sheet 2 Filed Dec. 30, 1947 ATTORNEYPatented Dec. 27, 1949 UNITED STATES PATENT OFFICE TUBE FORMINGAPPARATUS Ralph B. Thomas, Beverly, and Gerald S. Quinn, Salem, Mass,assignors to Sylvania Electric Products Inc., Salem, Mass., acorporation of Massachusetts Application December 30, 1947, Serial No.794,618 4 Claims. (01. 49-7) This invention relates to electric gaseousdischarge devices and more particularly to fiuorescent lamps of thecurved or circular type.

An object of this invention is to provide apparatus for accuratelyforming a substantially circular glass tube.

Another object of this invention is to provide apparatus for accuratelyforming a substantially circular glass tube from a helically formedsection of glass tubing.

A further object is to provide apparatus for accurately forming asubstantially circular fluorescent lamp from a helically formed sectionof glass tubing which has had its inner wall coated with a luminescentmaterial and electrodes sealed in the endsthereof.

Other objects advantages and features will be apparent from thefollowing description when read in conjunction with the accompanyingdrawings in which:

Figure 1 is a top plan view of one modification of the apparatus of myinvention;

Figure 2 is a front elevational view of the apparatus shown in Figure 1;

Figure 3 is a side elevational view of the apparatus shown in Figure 1;

Figure 4 is a fragmentary detail plan view showing the manner in whichone of the lamp lead Wires is secured to the base of the apparatus;

Figure 5 is a front perspective view of another modification of theapparatus of my invention;

Figure 6 is an enlarged perspective view of that portion of theapparatus of Figure 5 which accomplishes the formation of a circularglass tube from a length of helically formed glass tubing; and

Figure 7 is a front elevational view of the apparatus of Figure 5.

This invention embodies the idea of providing a flattening jig whereby alength of helically formed glass tubing, which has had its inner wallcoated with a luminescent material and electrodes sealed at each endthereof, may be formed into a circular lamp.

The manufacturing of a circular fluorescent lamp presents many problemswhich are not confronted in the manufacturing of conventional lineartype lamps. It is quite difiicultto start with a curved tube of theexact dimension and configuration finally desired because of thedifiiculties which would be encountered incoating the inner wall of thetube with luminescent material and sealing electrodes in the endsthereof. This would be so because the ends of the tube would be quiteclose to each other and in the same horizontal plane. Thus, far toolittle working area about the ends of the tube would be available foraccomplishing these operations.

Basically there are, in general, two sequences of manufacturingoperations possible. One may start with a conventional linear tube, coatit with luminescent material, seal electrodes in the ends thereof, andthen bend the tube to the desired form, or one may start with a helix ofseveral turns of tubing, cut it into several units of about one turneach, coat each unit with a luminescent material, seal the electrodes inthe ends thereof and then form the tube into the finally desired shape.In both cases the lamp is evacuated, a filling of inert gas isintroduced therein, and the exhaust tube sealed, after the tube has beenfashioned to the finally desired form.

The apparatus of this invention provides means whereby a helicallyformed unit of glass tubing which has had its inner wall coated with lu-.minescent material and electrodes sealed at each end thereof may beshaped into its final circular form prior to evacuation.

The unit on which this operation is performed is formed from single turnsections cut from a helix of glass tubing, with a space between the endsthereof preferably slightly less than the finally required spacing. Thepitch of the helix is predetermined so that the ends of each unit cuttherefrom will be offset from each other the desired amount. Althoughthis helically formed unit of glass tubing may be obtained by making asimple radial cut at the desired point on the helix, we have found itmore desirable to cut the tubing so that the end faces of the unit oftubing out are substantially parallel to a plane containing the axis ofthe helix and passing through the center of the space between the endsso cut. The inner wall of each unit is coated with luminescent materialand electrode mounts are sealed in each end thereof, at least one ofsaid mounts being provided with an exhaust tube through which the sealed.device may be evacuated. This. exhaust-tube is then bent at rightangles and perpendicular to the axis of the helix at a point along'itslongitudinal axis where it is disposed outside-the .re-entrant stem ofthe electrode mount. This is done to permit the positioning of the lampin. the flattening jig.

We have found it desirable to position this helically formed unit ofglass tubing on the fiattening jig with reference to a line runningthrough the center of the circle defined by the unit and through thecenter of the space between the ends of the unit as finally formed.

Referring now to the drawings, and more particularly to the embodimentillustrated in Figures 1, 2, 3 and 4, the flattening jig comprises abase plate I on which a lamp (the unit or section of tubing referred toabove) 2, is positioned, an adjustable yoke 3, a fixed stop 4, and anadjustable eccentric stop 5,, all of which are mounted on the base plateand which serve as guides in positioning the lamp 2 on the base plate, aclamping arm 6 pivotally mounted on the eccentric stop movement thereof,the purpose .for which 'will be described later.

In operation, the :lamp :2 is placed on the'base plate I with the endI;I thereof:abutting-the-stop 4, andthe exhaust tubulati'on 3-Iresting'on 'or .slightly above the :upper surface of .the stop 4. Oneofthe lead-wires 33 maythenbewoundfabout a stud 32 on the base .plate 2(Figure 4).. Although this is not necessary, it has been found desirablebecause itaids in securing .this end. of thelamp =in position. The otherlead wire should be bent outwardly substantially as shown in Figure "4so that it will not inteffere with the operation of the jig.

The-arm "I is then moved into position by causing the V-blockB to engage"the lamp 2 adjacent the-end II thereof. The V-block 9"is provided witha cam 20, the outer surface-of which engages the end I I of the lamp.

'The adjustable yoke 3 which is mounted on the base plate I servesasaninternal centeringgauge and is a means for centering the lamp '2 on thebase plate so that the center of the circle defined "by the lamp is on-alinepassing through the 'center of the space between the ends of thelamp,

The position of the lamp *2 on the'base plate "I is adjusted so thatboth ofthe arms -I3 of the yoke 3 touch the lamp. These two points ofcontact, in conjunction'with the disposition of the end II of the lampin contact with the 'stop 4, provide a three-point contact forpositioning the lamp. Although we have found the use of the adjustableyoke to be of assistance in accurately positioning the lamp "'2 .for theflattening operation we have also foundthat its use may .be dispensedwith and the lamp lined up .visually if .desired.

The eccentric stop 5 is then rotated until it touches the lamp 2. Theclamping arm "6 is then moved into positionto lock the lamp 2 tothe baseplate I (Figure .1). The "adjustable yoke 3, .if ,used, may then'beremoved from the jig.- The lamp '2 is now held in positron'on'the jig bythe stop 4, the :V-block 9, the eccentric stop *5 and the clamping arm'6.

As mentioned above each of .thearms1 and .8 have a weightedV-block 9hand Illtrespectively disposed on itsfree end. 'The 'v-block 9 isprovidedwith a cam 29 and the vblock II] is 'proit touches the baseplate I.

As mentioned above, the arm 8 is pivotally mounted in the plate I5 in amanner which will permit a small amount of horizontal angular movement.This is done to afford freedom of movement of the cam follower 2| and topermit adjustments to be made for small variations in the initialdistance between the :ends !I I and I2 of the lamp. The V-blocks 9 andI0 are properly positioned on the lamp 2 when the outer faces of 'cam 29and cam follower 2I respectively abut :the-ends II and I2 respectivelyof the lamp.

In order to prevent distortion of the cross sec- "tion of the lamp .2during the heating and fiattening operation the arm I is provided with asupport I6 'which'comprises a block II attached to the arml, a pin 'I'8extending through the block \III anda locking screw I9. After the arm Ihas beenpositioned the screw I9 is loosened to permit the pin I8 to dropdown in the block I! until The pin I3 is then "locked in this positionby the locking screw I9. Tn this 'way,the =V-block 9 still'engages thelamp 2 but its weight and the weight of the arm I 'is now carried bythe'pin I8.

The lamp 2 is now ready for the flattening operation. This assembly isthen placed in a heating chamber where it is exposed to heat of a degreecalculated to cause the glass, of which the lamp '2 is made, to softenand become plastic. When the glass softens the weighted V-block IE! willslowly, by force of gravity, push the raised and I2 of the lamp "2downwardly until the en- .tire lamp rests 'on'the'base plate 'I and theends .II and I2 thereof are 'in proper circular alignment andspaced thepredetermined distance.

In placing this assembly in a heating chamber it has beenzfounddesirable to elevate the side of the base plate which supports theraised end of the lamp about '8 degrees. This is done to insure apositive contact between the cam 20 and its 'follower'ZI as the 'end' I2of the lamp moves into position and to make sure that when thefiattening operation is completed the ends II and I2 of the lamp will bespaced the desiredpredetermined distance. This cantin'g is particularlydesirable in-cases where the distance between the ends of the lampinitially is greater than the finally desired distance because, when.the heated glass becomes plastic, gravity will cause the end of thelamp .I2 and the cam follower 2I to move until .the cam follower 2'I is.in contact with the cam '20. 'Thus the flattening operation may besatisfactorily performed on the apparatus of our invention .in caseswhere the ends of the tube are initially spaced a greater distance fromeach other than the finally desired distance as well as in cases wherethe ends are initially closer to each other than is finally desired.

A. ,plate .22 is mounted on top of cam follower -2I.. This plate :serves.as means for limiting the downward movement of the weighted vblock I0.and the cam follower .2.I durin the fiattening operation. After the endI2 of the lamp '2 hasheen caused to move downwardly so that the entirelamp .isin contact with the base plate I .it .is extremely undesirableto have the weighted .V-block .IIl continued to exertpressure on thelamp. When the flattening operation has been accomplished the plate '22will strike the top of the cam '29 on the V-block 9, thus limiting theV-block I5 from any further downward movement. Thus if the apparatuswere Dermitted to remain *in theheating chamber after the flattening ofthe lamp had been accomplished the plate 22 would serve "as asafetydevice to prevent the weighted V-block from continuing to exert pressureon the lamp and deformin the end thereof.

Referring now to the modification shown in Figures 5, 6 and '7, many ofthe principles embodied in the structure shown in Figures 1, 2, 3 and 4and described above are applicable to this structure. Similar referencenumerals have been used in Figures 5, 6 and 7 to designate elementswhich are the same as elements in Figures 1, 2, 3 and 4. The adjustableyoke 3 shown in Figure 1 has been omitted in this modification.

A lamp 2 is positioned on the instant structure in substantially thesame manner in which it was positioned on the Jig just described. Theend I I of the lamp is positioned so that its end surface abuts the stop4; the lamp is centered with reference to a line running through thecenter of the circle which it defines and the center of the spacebetween the ends of the lamp as finally formed; the eccentric stop isadjusted to cause it to engage the lamp; and the clamping arm is swungin to lock the lamp in position. The exhaust tube 3I is disposed on orabove the stop 4.

In the present structure the V-blocks 9 and I0 are mounted on posts 23and 24 respectively instead of on arms 1 and 8 as is done in theabovedescribed structure. The posts 23 and 24 are mounted on the baseplate I. The V block Ill is provided with channels 21 out in the sidesthereof, through which posts 24 extend. The weight of the V-block 9which was removed from the lamp by the arm support I6 in the previouslydescribed apparatus is removed in the present structure by means ofscrew 25 which extends through the V-block 9 and a wing nut 26. Afterthe end I I of the lamp 2 has been positioned the V-block 9 is mountedon the posts 23 and dropped down to engage the lamp. The screw 25 isturned down until it makes a positive contact with the top of post 23.Thus the weight of the V-block 9 is carried by the posts 23 instead ofthe lamp 2.

In the description of the first embodiment of this invention it waspointed out that the arm 8 which carried the V-block II! was pivotallymounted in a manner which permitted a small amount of angular movementin a horizontal plane to afford freedom of movement of the cam followerand to compensate for small variances in the initial distance betweenthe ends of the lamp and thereby permitted the V-block ID, in all cases,to be positioned on the lamp with the outer face of the cam follower 2!abutting the end I2 thereof. In the present structure the use of cam 28and cam follower 2| is dispensed with. Their function is now performedby the posts 24 which are not mounted perpendicular to the base plate Ibut rather at a pre-determined angle. This angular disposition of theposts 24 is calculated so that when the flatmning operation is completedthe stop 28, on the V-block I9, which abuts the end I2 of the lamp 2will have caused the lamp in its plastic condition to assume a positionin which the ends I I and E2 of the lamp will be in proper circularalignment and spaced the desired distance apart.

The adjustable screw 29 mounted in the bracket 30 which is attached tothe V-block Iii performs the same function as the plate 22 does in thestructure illustrated in Figures 1, 2, 3 and 4, i. e., when theflattening operation has been accomplished, the screw 29 engages the topof the V- block 9 and thus shifts the weight of the V-block Hi from theend I2 of the lamp to the V-block 9. This prevents distortion of thecontour of the lamp while it is plastic.

Thus the apparatus of our invention provides a means whereby one mayform a substantially circular fluorescent lamp from a unit cut from ahelix of glass tubing. We have found it desirable to start with a unitof tubing in which the ends are substantially parallel to a referenceplane containing the axis of the helix and passing through the center ofthe space between the ends. We

.have also found it desirable to form this unit of tubing so that whenthe operation has been completed the ends will be in circular alignmentwith no point on the principal plane of either end of the tube less thana pre-determined distance from a reference plane through the center ofthe circle defined by the tube and perpendicular to the plane of thecircle and passing through the center of the space between the ends.

However, it is to be understood that the principles herein enunciatedprovide the basis for the manufacturing of substantially circularelectric gaseous discharge devices in which the ends are not disposed inthe specific manner mentioned above without departing from the spirit ofthis invention, For example, it is not absolutely necessary that onestart with a unit of tubing in which the ends thereof are substantiallyparallel to a reference plane containing the axis of the helix andpassing through the center of the space between the ends. For example,one may well start with a unit of tubing in which the ends are formedfrom radial cuts. Similarly, it is not absolutely necessary that theends of the tubing as finally formed be in circular alignment.

This is a division of our abandoned application Serial Number 676,193,filed June 12, 1946.

What we claim is:

1. Apparatus for forming a substantially circular glass tube in whichall points on the axis of the tube are in the same plane, from a segmentof a helix of glass tubing, said apparatus comprising; a base member,means for positioning said tube on said base member, means for securingsaid tube on said base member, a pair of weighted members supported fromsaid base member, each being disposed in a position to engage the tubeadjacent a free end thereof, a cam mounted on one of said weightedmembers, and a cam follower mounted on the other weighted member andengageable with said cam.

2. Apparatus for forming a substantially circular glass tube in whichall points on the axis of the tube are in the same plane, from a segmentof a helix of glass tubing, said apparatus comprising: a base member,means for positioning said tube on said base member, means for securingsaid tube on said base member, a pair of weighted members supported fromsaid base member, each being disposed in a position to engage the tubeadjacent a free end thereof, a cam mounted on one of said weightedmembers, and a cam follower mounted on the other weighted member andengageable with said cam.

3. Apparatus for forming a substantially circular glass tube in whichall points on the axis of the tube are in the same plane, from a segmentof a helix of glass tubing, the ends of which are initiallysubstantially parallel to a reference plane containing the axis of thehelix and passing through the center of the space between the ends, saidapparatus comprising: a base member, means for positioning said tube onsaid base member, means for securing said tube on said base member, apair of weighted members supported from said base member, each beingdisposed in a position to engage the tube adjacent a free end there-01,2. oammounted'on oneofsaid weighted memcular glass tube in which allpoints on the aXis of the tube are in the same plane, from a segment ofa helix of glass tubing, said apparatus comprising: a base member, meansfor positioning :said tube on said base member, means for securing saidtube on said base member, a pair of weighted members supported from saidbase member, each being disposed in a position to engage the tubeadjacent a free end thereof, a cam 8 mounted on one of said weightedmembers, and a cam follower mounted on the other weighted member and.engageable with said cam.

RALPH B. THOMAS. GERALD S. QUINN.

REFERENCES CITED The following references are of record in the file ofthis patent:

FOREIGN PATENTS Number Country Date 539,291 Germany Nov. 24, 1931

